1. Field of the Invention
This invention relates to pressure vessels and, more particularly, to pressure vessels for containing fluids at very high pressures.
2. Description of the Prior Art
Vessels for containing fluids, at elevated pressure levels, are known. For example, U.S. Pat. No. 3,256,069 to O. A. Peterson discloses a pressure vessel structure which includes an inner vessel surrounded by a plurality of axially stacked, annular plates. The annular plates are clamped together by tie rods which extend axially through aligned bores in the plates, with nuts threaded onto the opposite ends of each tie rod. The inner walls of the annular plates closely surround the outer surface of the inner vessel and serve to reinforce the walls of the inner vessel, such that a fluid pressure of up to about 15,000 p.s.i. may be supported within the inner vessel.
Another prior art pressure vessel is disclosed in U.S. Pat. No. 3,278,993 to J. Brayman et al., and is said therein to be capable of supporting very high fluid pressures, e.g., 400,000 psi. In the Brayman et al. pressure vessel, a thin inner tube is surrounded by a cylindrical liner, composed of soft material, which is itself surrounded by a segmented outer support cylinder formed by a plurality of axially stacked ring layers. Each ring layer includes a plurality of arcuate ring sectors, with the sectors of adjacent rings angularly offset from one another. Several pins pass axially through aligned bores in adjacent, angularly offset sectors in order to interconnect the sectors into an integral assembly. The pin structure may also serve to clamp the ring layers axially together by utilizing pins which pass axially through the entire set of ring layers, and providing nuts, threaded onto the outer ends of the pins, to apply the necessary clamping force. Alternatively, external clamping bolts may be employed in addition to the interconnecting pins.
A further prior art pressure vessel is disclosed in U.S. Pat. No. 3,433,382 to F. G. Boggio, the Boggio patent and the previously mentioned Brayman et al. patent having been assigned to a common assignee. The Boggio patent indicates that the thin inner tube of the Brayman et al. pressure vessel is subject to failure under pressure. This problem is addressed in the Boggio pressure vessel by providing a structure wherein a liner tube is surrounded by a segmented outer support cylinder similar to the segmented outer support cylinder of the Brayman et al. pressure vessel, and wherein suitable additional mechanisms are employed to produce hoop tension stresses in the outer support cylinder and simultaneous hoop compression stresses in the liner tube, prior to introducing very high pressure fluid into the pressure vessel. The Boggio patent suggests some examples of mechanisms for pre-stressing the outer support cylinder and the liner tube in the described manner during assembly of the pressure vessel. In particular, a slight axial taper may be formed in the liner tube, and the tapering liner tube may thereafter be driven axially into the bore of the outer support cylinder. Alternatively, one or more wedges may be driven into appropriate slots in a hollow, cylindrical member positioned between the liner tube and the outer support cylinder.
The structure described in the Boggio patent, as is true also with respect to the structure described in the Brayman et al. patent when functioning properly, is capable of containing pressures significantly higher than those possible in the Peterson structure. However, the Boggio and Brayman et al. structures are considered relatively complex, and relatively costly to manufacture and assemble. Accordingly, the provision of a simple and relatively inexpensive, yet durable, pressure vessel configuration, capable of containing fluids at very high pressures, would clearly be desirable.